This invention relates to electromechanical apparatus adapted for sensing fuel levels and energy content of those fuels in a fuel container.
Conventionl fuel level sensors and systems typically utilize a float device or other surface level detecting scheme to provide information on the quantity of fuel in a container.
A novel approach utilizing a rate of pressure change in air above the surface of a liquid has been described in the Winter 1985 issue of NASA Tech Briefs, and is used to measure the volume of air of the surface, thereby providing information from which the volume occupied by the fuel may be readily calculated.
A significant drawback in all known prior systems and sensors is the limitation to volume determination. The actual energy content of the fuel has been typically computed on a per/unit volume basis, with the assumption inherent therein that the energy content per unit volume remains substantially constant.
A significant problem results in the environment where fuels of differing quality are regularly introduced into the fuel container, thereby substantially decreasing the accuracy of all fuel efficiency data based on volume. Additional secondary problems result from inaccurate fuel efficiency determinations such as cost per mile, in vehicular applications, difficulty in projecting the most cost effective and therefore fuel efficeint speed over varying terrain, and general cost control measures.
Accordingly, it is an object of the present invention to provide a fuel quantification system capable of determining both volume and quality with respect to fuel energy per unit volume.
Another object of the present invention is to provide a fluid measurement system capable of determining the specific gravity of a fluid in a tank, thereby allowing computation of energy content.
Briefly, and in accordance with the present invention, a fuel analysis system for a fuel container comprises at least two hydrostatic sensor means, each for providing a pressure output, a first output directly related to fuel quantity, and both sensors cooperatively providing outputs related to specific gravity of said fuel. The pressure diffference between first and second sensors constitutes a hydrostatic difference, with one sensor mounted at a higher gravitational potential that the other, which can be utilized in accordance with the present invention to ascertain specific gravity of the fuel. Thereafter, the specific gravity is computed either from a look-up table or directly through an analog process to cetane index. This provides a close approximation of the energy content of the fuel, as well as the quantity of the fuel in the tank.